









/ % ,--i>:*< a* «v^?*/ V'—"> < V^\/ V •"••• a* ** 

/.•afcX .0"*.iaat%.. y.-^itX .0»*.5^;.%.. >*,•-■ 



•bv* 





♦♦*% ■ 



a, ^ ♦'TV. 1 ,6 V ^o 








"b^ 
















^ 
# %/'^« # ^ ^ %* 







X *^a^ <^ 
^ <^ 'Asm,. <^ ^ *SlS^ a ^ «^ ••i 
> *v *^s •iclfgf* «^ ^, ovJIX^* a^ "^ • 

A> - « - , ^- 





> ^ '.' 




•• ^ 








4V ^» 





a °<v : 
















r oV 








^7^ 

- a v *^ : 





G v ^ -i".7* A 








HOft 











4* ^ 






<5°* 











^^ 













r > 



v t ^k* ^ aP 



^o x 










0^ t «^f*/ 








sP-nK 





^°^ v 




^ 




> ^ ,V si,/*???* o- 



A c o « o „ V 



A« a-*, o»»- ,A' ->-j. -v . s - r.- 













•*wE- /\ °Wws /\ \llf** /\ ^™* : *?% llpy «/% 

•^t.v .***£&>* ,s,<j^-:«+' \°*,^k-\ &£&&. v,^. 



&*■ n o » o 






c5°^ 



i0v\ 






A°* 



N 









•^••> 4 /.-^<X c°.^^,-> ,/.-^,t\ *°.i^: ^ / -^i- 




























BUREAU OF MINES 
INFORMATION CIRCULAR/1988 

it 



Rollover Protective Structure (ROPS) 
Performance Criteria for Large 
Mobile Mining Equipment 



By Stephen A. Swan 



UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9209 



Rollover Protective Structure (ROPS) 
Performance Criteria for Large 
Mobile Mining Equipment 



By Stephen A. Swan 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
T S Ary, Director 







* 



Library of Congress Cataloging-in-Publication Data 



Swan, Stephen A. 

Rollover protective structure (ROPS) performance criteria for large 
mobile mining equipment. 

(Information circular / United States Department of the Interior, Bureau of Mines ;9209) 

Includes bibliographical references. 

Supt. of Docs, no.: I 28.27:9209 

1 . Mining machinery — Rollover protective structures. 2. Loaders (Machines) — Safety appli- 
ances. I. Title. II. Series: Information circular (United States. Bureau of Mines) ;9209. 



TN295.U4 [TN345] 622s [622'. 8] 88-600283 



CONTENTS 



Page 

Abstract 1 

Introduction 2 

Test procedures 2 

Roll hill characteristics 2 

Roll hill slope and vertical drop height 2 

Roll hill length 3 

Roll test procedures 3 

Method of release 3 

Launch pad 3 

Bucket position 4 

Articulation joint 4 

Instrumentation and measurement 

parameters 4 

Data link and sensor types 4 

Strain 4 

Deflection 5 

Acceleration 5 

Roll rate 5 

Time 5 



Page 

Tests with 52,000-lb-GVW, wheeled, 

front-end loader 5 

Roll test 1 5 

Roll test 2 6 

Tests with 390,000-lb-GVW, wheeled, 

front-end loader 8 

Roll test 3 8 

Roll test 4 9 

Static test of four-post ROPS 10 

Test with 286,000-lb-GVW, wheeled, 

front-end loader 13 

Conclusions 14 



ILLUSTRATIONS 

1. Equivalent rollover, 720° 3 

2. Tilt table 4 

3. Instrumentation schematic 5 

4. ROPS before and after rollover, 52,000-lb-GVW, wheeled, front-end loader 7 

5. First 390,000-lb-GVW, wheeled, front-end loader after rollover 9 

6. Mount failure, 390,000-lb-GVW, wheeled front-end loader 9 

7. Second 390,000-lb-GVW, wheeled front-end loader before and after rollover 10 

8. Static test side load deflection curve, 390,000-lb-GVW, wheeled, front-end loader 11 

9. Static test vertical deflection curve, 390,000-lb-GVW, wheeled, front-end loader 11 

10. Static test longitudinal load deflection curve, 390,000-lb-GVW, wheeled front-end loader 12 

11. Roll test 5, 286,000-lb-GVW, wheeled front-end loader 13 



TABLES 



1. Parameter measuring sensors 4 

2. First roll test summary 6 

3. Second roll test summary 6 

4. Third roll test summary 8 

5. Fourth roll test summary 10 

6. ROPS static test side and longitudinal load energy 12 

7. Fifth roll test summary 14 





UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 


°/s 


degree per second lb pound 


ft 


foot pet percent 


g 


acceleration of gravity psi pound per square inch 


in 


inch s second 


in'lb 


inch-pound 



ROLLOVER PROTECTIVE STRUCTURE (ROPS) PERFORMANCE CRITERIA 
FOR LARGE MOBILE MINING EQUIPMENT 



By Stephen A. Swan 



ABSTRACT 

Certain types of mobile surface mining equipment are required to be equipped with 
rollover protective structures (ROPS) capable of protecting the operator in case of a rollover 
accident. The Bureau of Mines has developed ROPS performance criteria for wheeled 
front-end loaders. This report reviews the development of rollover test procedures and 
subsequent testing of ROPS for 52,000-, 286,000-, and 390,000-lb gross vehicle weight 
(GVW) loaders. The program consisted of both dynamic (roll) and static tests to assist in the 
development of the ROPS performance criteria. Each test included extensive instrumentation 
and photographic documentation to fully evaluate the performance of the ROPS. Data 
summarizing side, longitudinal, and vertical force and deflections are included. The data 
indicate that for loaders in excess of 240,000 lb, GVW, a side force-to-mass ratio of 1.0 and 
an energy-to-mass ratio of 6.0 appear to be adequate criteria to protect an operator in the 
event of a 540° rollover. For smaller machines, Society of Automotive Engineers (SAE) J 1040 
performance criteria provide adequate protection. Longitudinal loading, though not ad- 
dressed in previous ROPS performance criteria, was shown to be a potentially significant 
factor in ROPS failure. Longitudinal loading and energy criteria equal to 80 pet of side 
loading criteria are recommended. 

1 Mining engineer, T\vin Cities Research Center, Bureau of Mines, Minneapolis, MN. 



INTRODUCTION 



Mine Safety and Health Administration (MSHA) and 
Occupational Safety and Health Administration (OSHA) reg- 
ulations require that certain types of mining, construction, 
earthmoving, agricultural, and forestry equipment be 
equipped with a rollover protective structure (ROPS). The 
types of mobile machines that must be equipped with ROPS 
include crawler tractors and crawler loaders, motor graders, 
wheeled loaders and tractors, skid-steer loaders, and the 
tractor portion of tractor-scrapers. Although not mandated by 
regulation, ROPS are sometimes installed on off- highway 
haulage trucks and water trucks. 

The requirement of ROPS regulations in the United 
States, Canada, and other countries is due to the significant 
injury potential represented by accidental rollovers of mobile 
equipment during field use. The use of ROPS and seatbelts on 
these types of equipment can greatly reduce the number and 
severity of injuries resulting from rollover accidents. Although 
the regulations require that the employer who owns the 
machine equip it with ROPS to provide a safer work environ- 
ment for employees, manufacturers of the machines typically 
install ROPS on the machines before ownership is transferred 
to the employer. 

The Society of Automotive Engineers (SAE), through 
Subcommittee 12 — Off Road Machinery Technical Committee 
(ORMTC), develops ROPS structural performance and test 
method criteria for use by industry in the design and perform- 
ance certification of ROPS used on construction and mining 
machines. The ROPS regulations promulgated by OSHA and 
other regulatory bodies base ROPS structural performance 
capability on criteria developed by SAE. 

In 1972, ORMTC began development of SAE Recom- 
mended Practice J 1040 "Performance Criteria for Roll Over 
Protective Structures (ROPS) for Construction, Earthmoving, 
Forestry, and Mining Machines." However, because of the 



absence of rollover test data, the force-energy criteria for 
machines exceeding 132,000 lb gross vehicle weight (GVW) 
were projected based on the collective judgment of the com- 
mittee. The committee reasoned that ROPS force-energy cri- 
teria, expressed as a function of total machine size and weight, 
could be less for large machines than for small machines. The 
lower requirement was possible because the operator compart- 
ment on a larger machine is smaller, in proportion to total 
machine size, than for a small machine. As a result, when a 
large machine rolls, a greater proportion of the energy gener- 
ated by the roll would be absorbed by the machine body, tires, 
frame, etc., than would be the case for a small machine. 

In 1977, rollover test data were produced indicating that 
the force and energy requirements contained in the SAE J 1040 
recommended practice were not sufficient for large machines. 
A machine manufacturer performed ROPS rollover tests on a 
front-end loader and crawler tractor, each weighing approxi- 
mately 200,000 lb. Although both ROPS exceeded SAE J 1040 
performance criteria, neither survived the roll test. SAE sub- 
sequently informed OSHA that the validity of the force and 
energy requirements delineated in J 1040 was in doubt and 
recommended that new guidelines be developed for larger 
construction and mining machines. An interim guideline, SAE 
J1040c, was established by ORMTC, however it, like its 
predecessor, was based on subjective judgments and extrapo- 
lation from available test data. As larger and heavier front-end 
loaders were introduced (up to 390,000 lb), the adequacy of 
these judgments and extrapolations was seriously questioned. 
This report documents research to establish ROPS perform- 
ance criteria for large front-end wheeled loaders through a 
systematic program of dynamic (roll) and static testing. The 
test program involved trials with loaders weighing 52,000, 
286,000, and 390,000 lb. The research was performed by 
Woodward Associates, Inc., under contract to the Bureau. 2 



TEST PROCEDURES 



Because the objective of the program was the establish- 
ment of ROPS performance criteria for large front-end 
wheeled loaders without reliance on subjective judgments and 
extrapolation from tests of smaller machines, emphasis was 
placed on full-scale testing of ROPS under realistic, yet 
controlled and reproducible conditions. Roll testing, wherein a 
host machine equipped with a fully instrumented ROPS is 
caused to roll down an embankment, is the most realistic test 
possible, as it nearly duplicates field conditions. However, not 
all test variables can be easily controlled. Thus, "identical" 
rolls may produce a range of data values that require consid- 
erable interpretation to provide meaningful results. Static 
testing, wherein the ROPS is installed in a load frame that 
applies measured loads of known magnitude and direction, 
produces results which are more reproducible and there is less 
uncertainty in the data. However, the magnitude and direction 
of the loads that must be applied in order to predict ROPS 
performance under field conditions are not always known. 
Roll testing is also significantly more costly than static testing. 

As a result of these considerations, a test plan was devised 
that incorporated both roll testing and static testing. ROPS 
performance criteria would be based on the combined results 
of the two procedures. Depending on the degree of correlation 
between results of the roll and static testing, it was also hoped 
that greater reliance could be placed on static testing in the 



future, perhaps in conjunction with computer simulation, as a 
way of reducing the cost of assessing the performance capa- 
bility of ROPS structures. 

The following sections describe the characteristics of the 
test fixtures and equipment and the procedures utilized during 
the test program. 



ROLL HILL CHARACTERISTICS 

Roll Hill Slope and Vertical Drop Height 

Two considerations govern selection of roll hill slope: side 
loading of the ROPS at initial impact and continuation of the 
roll to achieve at least 360° machine rotation. The critical 
design load for a ROPS is generally in the side direction 
because of high bending stresses in the support members. 
Thus, shallower slopes that maximize side loading of the 
ROPS at initial impact are favored by some equipment man- 
ufacturers. SAE J 1040c stipulates a 30° maximum slope to 



2 Dahle, J. L., and G. R. Gavan. Development of Rollover Protective 
Structures (ROPS) Performance Criteria for Large Mobile Mining Equipment 
(contract H0292020, Woodward Associates, Inc.). BuMines OFR 57-86, 1985, 
277 pp.; NTIS PB 86-216066. 



insure high initial side loads. However, if the slope is too 
shallow, the machine simply tips over and slides down the 
slope without rolling. The manufacturers with the most roll 
testing experience favored 30° to 40° slopes because they 
found the machines would reliably roll only on steeper slopes. 
It was concluded that a compromise roll hill slope of 35° 
would produce acceptable initial side loading while insuring at 
least 360° roll rotation. 

Another test parameter related to roll hill slope is the 
vertical drop height from the launch pad to the slope. Low 
vertical drop heights, like shallow roll hill slopes, introduce 
high initial side loads, which is desirable. However, higher 
drop heights induce greater angular momentum in the ma- 
chine, which is necessary to cause rotation and successful 
rolling. Analysis indicated a 30-in vertical drop height would 
produce the desired results. 

Roll Hill Length 

There was general agreement among the manufacturers 
consulted that the length of the roll hill should be based on two 
factors — the perimeter of the machine to be rolled and the 
number of expected rolls. It was recommended that an addi- 
tional 30 pet of hill length would be required to account for 
any machine slippage during the roll. Therefore, it was deter- 
mined that a length of 120 ft would accommodate a minimum 
of 720° of roll from the smallest to the largest machine to be 
tested (fig. 1). 



ROLL-TEST PROCEDURES 

All manufacturers consulted agreed that the machine 
should be positioned at the top of the slope with the outermost 
wheels at the edge of the slope. The machine would then be 
tipped to the side to initiate roll down the hill. This method, as 
opposed to the machine having a forward motion when tipped 
over the edge of the hill, would provide for the best repeat- 
ability of test conditions. 



Method of Release 

The machine was positioned at the top edge of the slope 
on a tilt table. The side of the platform away outboard from 
the edge of the roll hill was elevated (fig. 2) and the machine 
rolled off the platform when the center of gravity passed 
beyond the inboard tires. The advantage of using a tilt table, in 
addition to providing repeatable release conditions, was that it 
could be reused for other testing. 



Launch Pad 

A launch pad for the machines was necessary in order to 
provide the method of release as described above. The inboard 
side of the tilt table had to be pinned to the structure in order 
to rotate. In addition, as the machine is being tipped all of its 



Roll initiation 



Initial side load contact of ROPS first impact 




Second side load contact 



Final contact of ROPS 



Figure 1. — Equivalent rollover, 720* 



Outboard 



Lift point 



Inboard 
.: tire 




no,.- 






°°:ol 






& 



OflpV 









40' 



Concrete 
pad 



Figure 2. — Tilt table. 



weight is on the two inboard tires. A launch pad or footing was 
necessary to prevent the edge of the hill from slipping or falling 
away (fig. 2). 

Bucket Position 

During all tests the bucket was locked and welded in the 
carry position as defined by SAE J732c. This definition 
requires the bucket to be tipped backward to a 15° approach 
angle. 

Articulation Joint 

The articulation on all three machines was locked by the 
transportation locking bars and additional supports were 
welded in place. Again this was to provide for a repeatable test. 



the best data link. The recording system and components were 
based on the use of this method. 

Once the measurement parameters were determined, as 
described in the following sections, it was possible to select the 
type of sensors necessary to meet the program objectives. The 
sensors selected to measure the parameters are listed in table 1 . 

Table 1.— Parameter measuring sensors 



Instrumentation 

Accelerometer 

Potentiometer 

Rate gyroscope 

Strain gauge 

Time generator 



Umb 


ilical 


Front 


Rear 


3 


3 


3 


3 


1 


1 


10 


10 


1 


1 



Channels 



6 
6 
2 
20 
2 



INSTRUMENTATION AND MEASUREMENT 
PARAMETERS 

Data Link and Sensor Types 

The type of data link was an important factor in estab- 
lishing the other components of the instrumentation system. It 
was necessary to define the data link early in the planning of 
the instrumentation system (fig. 3). The types considered were 
the umbilical (hard-line) type or a telemetry system with 
AM-FM transmission. The umbilical system was selected as 



Strain 

Strain was considered to be the most important parameter. 
Of the 36 channels to be recorded, 20 were strain measurement. 

Some structural columns were instrumented with strain 
gauges on opposite sides of the column. These opposing 
gauges were wired into a single bridge, which permitted the 
measurement of bending with a single output. This method 
maximized the information gained from a smaller number of 
recorded channels. It was necessary to locate the gauges in 
areas that would not be subjected to local yielding. All strain 



Accelerometer 
(3 each) 



Potentiometer 
(3 each) 



Rate gyro 
(I each) 



Strain gauge 
(10 each) 



o 



| Bridge 






Umbilical 



completion 




Oscillograph 



To camera -^, 
timing * ^> 
circuits 



Time 
generator 



Figure 3. — Instrumentation schematic. 



gauges were wired with a three-wire hookup, and precision 
bridge-completion resistors were located on the machine near 
the strain gauge locations. All gauges were 1-in uniaxial 
gauges. 

Deflection 

Six channels were utilized to measure deflection of par- 
ticular locations on the ROPS. The measurements were made 
with resistive, linear position transducers with a 20-in stroke. 
The diagonal spans across the ROPS columns were measured 
in three planes to resolve the relative motions of the structure. 

Acceleration 

Six channels of acceleration were measured and recorded. 
The accelerometers were mounted in a triaxial configuration at 
two locations on the machine. The accelerometers had a range 
of ±20 g. 



Roll Rate 

This measurement was a direct result of the manufactur- 
er's survey information. One manufacturer was recording roll 
rates routinely on all roll tests to provide correlation from one 
test to the next. Roll rate is used to determine differences in roll 
test results. Acceleration measurements can also be used in this 
manner, but roll rate is a more positive comparison method. 
Two channels were utilized to record roll rate. 

Time 

Each oscillograph recorder was equipped with an internal 
time base that was recorded on each individual record. In 
addition, a time base generator for the cameras was recorded 
on the film edge, as well as on the oscillographic records. 
Flashbulbs in the view of all cameras were activated at the 
beginning of the roll to correlate a starting time. 



TESTS WITH 52,000-lb-GVW, WHEELED, FRONT-END LOADER 



ROLL TEST 1 

The rollover test of a 52,000-lb-GVW, wheeled, front-end 
loader equipped with a four-post ROPS that had a 106- 
pct-GVW (55,120-lb) side load capability successfully met the 
objectives of the roll test. The combination of the tilt table and 
the relative location of the launch pad and the roll hill 
provided an excellent method for roll initiation, which resulted 
in a relatively high side load on initial impact. The ROPS was 
subjected to three impacts during the test. Two impacts 
occurred on the roll hill and one impact occurred on the bench 
at the base of the hill. 

Table 2 summarizes the data obtained from the test. The 
data indicate that the structure was subjected to successively 
greater loads with each impact. The strain gauge data indicate 
vertical loadings of approximately 200 to 400 pet GVW, 300 to 
500 pet GVW, and 700 pet GVW for the first, second, and 
bench impacts, respectively. The vertical loading estimated 



from the soil resistance and accelerometers measurements 
indicates even higher vertical loads. 

The strain gauge data indicate a side load of 58,000 and 
60,800 lb for the first and the second impacts. The side load 
could not be determined for the bench impact. The ROPS had 
a side load capability of approximately 55,100 lb, as deter- 
mined by a static test conducted by the manufacturers of a 
similar unit. The measured side loads were thus higher than the 
estimated capacity of the ROPS. The discrepancies are prob- 
ably caused by measurement inaccuracies during the static and 
roll tests, and differences in the cross-sectional geometry and 
yield strengths of the two ROPS. The side loads for the first 
two impacts determined from the side deflections of the ROPS 
were approximately 50,800 and 52,800 lb. 

Estimated vertical and side loads, and estimated side 
deflection, are also given in table 2. These estimates are based 
on the data obtained from the test, considerations of the 
reliability and accuracy of the particular measurements, the 



capacity of the mounting bolts, and the observations of the 
high-speed film. 

The evaluation of the data obtained from the roll test 
indicated that the ROPS experienced vertical and side loads 
that exceeded the requirements of SAE J1040c. For compari- 
son, SAE J 1040c requires the following loads and deflections 
during static testing for the machine and ROPS that were 
subjected to the roll test: Side load, 73 pet GVW; side 
deflection, 13 in; and vertical load, 200 pet GVW. 

The static test required by SAE J 1040c is to provide 
protection for a 360° roll on a 30° slope. The ROPS that was 
subjected to the roll test meets these requirements. 

From the data and review of the impacts of the test, major 
structural damage to the ROPS appears to have occurred as a 
result of the third (bench) impact. The damage included tensile 
failure of the two 7/8-in, grade 8 mounting bolts at each rear 
post of the ROPS; tensile failure of the three 3/4-in, grade 8 
mounting bolts at the right-front post (the three 3/4-in bolts of 
the left-front post were not fractured); buckling of the rear 
plate (between the two rear posts) in the area where an access 
hole was cut; fracture of the top front crossmember and top 
plate; yielding of the complete cross section at the top of all 
four posts just below the gussets; and weld failure at the right 
mounting bracket for the instrument panel-ROPS attachment. 
Figure 4 shows the ROPS configuration before and after the 
roll test. 

Table 2.— First roll test summary 

(52,000-lb-GVW, wheeled, front-end loader) 

1st impact 2d impact Bench impact 



MEASURED 
Vertical load, 10 3 lb: 

ROPS strain gauges 

Soil resistance 

Acceleration 

Side load, 10 3 lb: 

ROPS strain gauges 

Soil resistance 

ROPS deflection 1 

Longitudinal load, 10 3 lb: 

ROPS strain gauges 

Side deflection, 2 in: 

Potentiometers 

Physical measurement.. 
Roll rate, s °/s: 

Accelerometers 

Gyroscopes 

Ground resistance, psi: 

Penetrometer 

Max ROPS penetration, in: 

Field measurement 

ESTIMATED 
Vertical load: 

Force 10 3 lb.... 

Force pet GVW.... 

Side load: 

Force 10 3 lb.... 

Force pet GVW.... 

Side deflection in.... 



115-203 

159 

208-260 

58 

40 

50.8 

15.14 

3 4.43 
3.25 

75 
106 

142 

24 



160 
310 

51 
98 
4.4 



147-237 

192 

156-312 

60.8 
44.3 
52.8 

9.78 



377 

3,400 

520 

ND 
ND 
ND 

ND 



5.25 


3 4 >24 


3.80 


>24 


90 


160 


120 


325 


157 


3,000 


19 


ND 


210 


>377 


400 


730 


53 


>55 


102 


106 


5.3 


24 



The operators platform to which the ROPS was mounted 
was damaged only in the area of the mounting bolt holes. 
Other machine damage was minimal. However, the left-rear 
tire rim seal was damaged and loss of pressure occurred. 

As indicated by the ground resistance and ROPS penetra- 
tion data in table 1 , the roll hill was very "soft" and the bench 
was extremely compacted. 



ROLL TEST 2 

The second rollover test of the 52,000-lb, wheeled, front- 
end loader and a four-post ROPS with a 120-pct-GVW side 
load capability successfully met the objectives of the roll test. 
Similar to the first test, the ROPS was subjected to two 
impacts during the test on the roll hill. The ROPS mounts did 
not fail during the test. 

Table 3 summarizes the data obtained from the second 
test. The data indicate that the ROPS was subjected to 
successively greater loads with each impact. The strain gauge 
data indicated vertical loadings of approximately 170 and 180 
pet GVW for the first and second impact, respectively. The 
vertical loadings estimated from the accelerometer measure- 
ments for each impact indicated vertical loads of 1.4 and 4.2 
pet GVW, respectively. Table 3 also contains estimated vertical 
and side loads, and estimated side deflection, based on data 
collected during the test. 

The strain gauge data indicated a side load of 57,700 lb 
(1 10 pet GVW) and 62,800 lb (120 pet GVW) for the first and 
second impacts. The measured side load during the second 
impact is higher than the estimated capacity of the ROPS. The 
structure had a side capability of approximately 120 pet GVW 

Table 3.— Second roll test summary 

(52,000-lb-GVW, wheeled, front-end loader) 



1st impact 



2d impact 



ND Not determined. 

1 Static test curve. 

2 Plastic 3d impact method. 

3 Maximum. 

4 Estimated, sensors reached maximum at 12 pet of full scale. 

5 Measured using average strain gauges and instantaneous pictures. 



MEASURED 
Vertical load, 10 3 lb: 

ROPS strain gauges 

Accelerometer 

Side load, 10 3 lb: 

ROPS strain gauges 

ROPS deflection 

Longitudinal load, 10 3 lb: 

ROPS strain gauges 

Roll rate, °/s: 
Before impact: 

Gyroscope 

Film 

After impact: 

Gyroscope 

Film 

Max ROPS penetration, in: 

Field measurement 

ESTIMATED 
Vertical load: 

Force 10 3 lb.... 

Force pet GVW.... 

Side load: 

Force 10 3 lb.... 

Force pet GVW... . 

Side deflection in.... 

ND Not determined. 
1 Off scale. 



87.45 
72.8 

57.7 
49 

10.55 



102 
113 

75 
87 



18 



87.5 
170 

57.7 

110 

>4.5 



94 
218 

62.8 
ND 



O 
318 

C) 
273 

16 



94 
180 

62.8 
120 
>13 



as determined by the static test results of a similar unit, 
corrected by the material strength allowables established after 
the roll test. This estimate is also based on the fact that the 
mounting bolts that failed during the static test were replaced 
with standard production bolts. 

The side load for the first impact as determined from the 
side deflections of the structure was approximately 49,000 lb. 
This side force was determined from the deflections measured 
from the high-speed film. The displacement transducers ap- 
peared to give inaccurate deflection measurements (approxi- 
mately 1 in) because some of the linear potentiometer mount- 
ing studs were bent. Therefore, the side forces determined from 
the deflections are not as reliable as those determined from the 
strain gauge data. 



Changing the roll hill penetration resistance from 150 psi 
for the first test to 1 ,800 psi for the second test appears to have 
affected the dynamics of the roll more than any other factor. It 
was expected that an increase in penetration resistance of the 
hill would have caused an increase in the vertical loads on the 
structure. In fact, however the vertical loads on the harder hill 
were only about one-half the loads that resulted from rolling 
the machine on the softer hill. The harder hill allowed the 
machine to gain angular momentum from the first to second 
impact thereby reducing the vertical loads. The angular mo- 
mentum entering the second impact was 2.8 times greater on 
the harder hill than on the softer hill. This was observed by 
comparing the high-speed film of the second impact for both 
tests. 









Figure 4. — ROPS before (top) and after (bottom) rollover, 52,000-lb-GVW, wheeled, front-end loader. 



TESTS WITH 390,000-lb-GVW, WHEELED, FRONT-END LOADER 



ROLL TEST 3 

The first rollover test of the 390,000-lb-GVW, wheeled, 
front-end loader with a four-post ROPS met the objectives of 
the test. The side of the machine contacted the roll hill before 
the ROPS did, which introduced maximum side loading of the 
structure. The machine rolled two complete revolutions on the 
roll hill, subjecting the structure to two impacts, and landed 
upright at the base of the hill. The data needed to analyze the 
behavior of the ROPS during the roll test were obtained and a 
summary of the results is given in table 4. 

The results indicate that the first impact imposed approx- 
imately a 110-pct-GVW side load (448,000 lb) on the ROPS. 
This is supported by the strain gauge data and also from the 
measured deflections. The strain gauge data show an equal 
distribution of the side load on the front and rear of the 
structure. A load-deflection curve generated from the com- 
puter analysis provided a means to correlate side deflection to 
applied load. 

The strain gauge data also show approximately a 190- 
pct-GVW vertical load (727,000 lb) for the first impact. The 
accelerometer data show a 4.9-g (1,911,000-lb) loading. This 
loading is predictably higher because only part of the machine 
weight contributed to the vertical loading. In this test the 
reduced vertical loading is mainly due to the top corner of the 
machine's frame absorbing part of the vertical force because it 
impacted the roll hill first and was still in contact with the 
ground when the ROPS hit. 

The longitudinal load during the first impact, as deter- 
mined from the strain gauge data, indicates about a 30- 
pct-GVW rear load (130,000 lb), consistent with previous tests. 

Table 4.— Third roll test summary 

(390,000-lb-GVW, wheeled, front-end loader) 



1st impact 



2d impact 



MEASURED 
Vertical load, 10 3 lb: 

ROPS strain gauges 

Accelerometer 

Side load, 10 3 lb: 

ROPS strain gauges 

ROPS deflection 1 

Longitudinal load, 10 3 lb: 

ROPS strain gauges 

ROPS mount failure 

Roll rate, °/s: 

Before impact: Gyroscope 

After impact: Gyroscope 

Max ROPS penetration, in: 

Field measurement 

ESTIMATED 
Vertical load: 

Force 10 3 lb.... 

Force pet GVW.... 

Side load: 

Force 10 3 lb.... 

Force pet GVW.... 

Longitudinal load: 

Force 10 3 lb.... 

Force pet GVW.... 

1 Computer load deflection curve. 



727 


1,014 


1,911 


1,755 


448 


398 


429 


526 


58 


390 


ND 


367 


108 


204 


42 


73 



47 



70 



727 


1,028 


186 


264 


448 


390 


115 


100 


130 


390 


30 


100 



Between the first and second impacts the machine devel- 
oped an angle of about 45° to the vertical centerline of the hill, 
measured from the impact impressions on the hill. Thus, when 
the ROPS impacted the hill it was subjected to equal longitu- 
dinal and side loads, which is confirmed by the strain gauge 
data. The longitudinal and vertical loads were at approxi- 
mately 100-pct-GVW (390,000 lb). The vertical load was 
determined to be about 260-pct-GVW (1,028,000 lb) from the 
strain gauges. 

The ROPS was designed for the following loads: Side 
load, 175 pet GVW; and longitudinal load, at one-third point 
on top 99 pet GVW crossmember. 

Although the ROPS survived the 360° roll, it did not 
survive the 720° rollover (fig. 5). The large longitudinal load 
and the manner in which it was applied to the ROPS during the 
second impact caused failure of the mount at the left rear post 
(fig. 6). The loads determined for the second impact are just 
prior to the failure of this mount. Despite the mount failure, 
the data indicate the structure was loaded to approximately the 
designed longitudinal load level. However, the mount failure 
prevented the ROPS from absorbing most of the energy 
associated with plastic deformation. 

Analysis of the test data and film showed that the 
longitudinal load for the second impact of this test was not 
applied in a manner consistent with current design philosophy. 
It appears that for large machines the ROPS penetration into 
the soil is extremely deep (70 in for the second impact). The 
deep penetration in combination with the machine developing 
a 45° angle to the vertical centerline of the hill in effect caused 
the ROPS to "plow" through the soil. 

The plowing action effectively distributed the longitudinal 
load along the post and to a lesser extent across the top 
crossmember of the ROPS. This effectively lowers the height 
of the resultant load, with the following results: 

For loads applied at the top of the ROPS from the rear, 
the reactions at the bottom of the posts are evenly distributed 
front and rear. 

When the applied load is effectively shifted to one side, 
the reactions at the bottom of the posts increase on the side 
that is loaded. 

When the applied load is effectively lowered, the reactions 
at the bottom of the post are redistributed with the horizontal 
reactions on the rear posts increasing and the horizontal 
reactions of the front post reduced. 

The change in the load application point from the top 
crossmember (at the one-third or one-quarter point) to along 
the post does not change the overall capability of the structure. 

A failure analysis showed that the mounts had the capa- 
bility of supporting a 150-pct-GVW longitudinal load if the 
load was applied at the top crossmember of the structure. That 
is, the mounts were 50 pet stronger than the ROPS. However, 
for a load distributed on the ROPS post, simulating the test, 
the capability of mounts (94 pet GVW) is slightly less than that 
of the ROPS. The strain gauge data indicated that the ROPS 
was subjected to a 100-pct-GVW longitudinal load before the 
mount failed. 

The results of this rollover test confirmed a design philos- 
ophy that ROPS mounts must have the structural capability to 
allow large plastic deformations in order to absorb the impact 
energy. However, the location of the longitudinal impact load 
on the ROPS did not occur as anticipated. The deep penetra- 
tion into the soil, in combination with the machine developing 
a 45° angle, caused the longitudinal load to be distributed 








Figure 5. — First 390,000-lb-GVW, wheeled, front-end loader after rollover. 




Figure 6. — Mount failure, 390,000-lb-GVW, wheeled, front- 
end loader. 



along the post instead of along the top crossmember. This 
effectively concentrated more of the load on one post instead 
of a more even distribution on all four posts. 

ROLL TEST 4 

The second roll test of the 390,000-lb-GVW, wheeled, 
front-end loader met the objectives of the test. Data were 
obtained to determine the magnitudes and direction of loading 
on the ROPS (table 5). The machine rolled two complete 
revolutions and subjected the ROPS to two impacts on the roll 
hill. 

The machine dynamics were very similar to those of the 
previous test of the same machine. The major difference was 
the fact that the longitudinal centerline of the machine only 
changed about 19° before the second impact as opposed to 45° 
in the previous test. This meant that there was a smaller 
longitudinal load on the ROPS during the second impact. 
Figure 7 shows the ROPS before and after the test. 

The strain gauges provided impact load data for the 
vertical, side, and longitudinal directions. The displacement 
potentiometers provided data to determine loads for only the 



10 



Table 5.— Fourth roll test summary 

(390,000-lb-GVW, wheeled, front-end loader) 



1st Impact 



2d Impact 



811 


1,015 


801 


1,158 


604 


616 


508 


576 



50 

118 
40 

57 



189 

218 
67 

84 



811 


1,092 


210 


280 


604 


616 


155 


158 


50 


189 


13 


48 


1.5 


3.0 



MEASURED 
Vertical load, 10 3 lb: 

ROPS strain gauges 

Accelerometer 

Side load, 10 3 lb: 

ROPS strain gauges 

ROPS deflection 1 

Longitudinal load, 10 3 lb: 

ROPS strain gauges 

Roll rate, °/s: 

Before impact: Gyroscope 

After impact: Gyroscope 

Max ROPS penetration, in: 

Field measurement 

ESTIMATED 
Vertical load: 

Force 10 3 lb.... 

Force pctGVW.... 

Side load: 

Force 10 3 lb.... 

Force pctGVW.... 

Longitudinal load: 

Force 10 3 lb.... 

Force pctGVW.... 

Av side deflection in.... 

1 Static test curve. 



side direction and accelerometer data provided loads for the 
vertical direction. The strain gauges provided a means to 
determine the loads by a standard method of data reduction. 
However, the reduction of the accelerometer data and the 
displacement potentiometer data required consideration of the 
machine dynamics in order to obtain meaningful results. 

In using the accelerometer data to calculate a vertical 
load, an effective mass of the machine acting on the ROPS 
during the impacts had to be assumed. Correlating the vertical 
loads and accelerometer data from previous tests indicates that 
for this test approximately 40 pet of the machine weight 
contributed to the vertical load on the ROPS. Therefore, 40 
pet of the machine mass times the measured vertical accelera- 
tion of the machine was used to calculate the vertical load on 
the ROPS. This correlated closely with the strain gauge data. 

The deflection data are difficult to use in determining the 
applied side load. The location of the side load during a roll 
test and static test will invariably be different. Thus, the 
deflections measured during a roll test cannot be directly used 
to correlate loads using the static test curve. However, an 
attempt was made to estimate the effects of the different load 
locations. In addition, the deflections were adjusted because 
of the geometry effects caused by potentiometer locations. 



STATIC TEST OF FOUR-POST ROPS 

The static testing of the four-post ROPS for the 390,000- 
lb-GVW, wheeled, front-end loader met the objectives of the 





^675 



; ; ; " 5 





f • 4 1-^ 




Figure 7. — Second 390,000-lb-GVW, wheeled, front-end 
loader before (top) and after (bottom) rollover. 



test. Load deflection curves were obtained for the side, verti- 
cal, and longitudinal directions. The energy absorbed by the 
ROPS was determined for the side and the longitudinal load 
tests. The loading sequence was as follows: 

Side-load. — On the side opposite the roll test loads to 
minimize the effects of possible frame damage. 

Vertical load. 

Longitudinal load. — Rear load at the one-quarter point 
on the same side of the ROPS as the side load. 

During the side load test the ROPS was subjected to a 
load of 685,100 lb. The ROPS deflected a total of 8.5 in and 
absorbed 4,179,000 in*lb of energy. The load deflection curve 
for the side load test is shown in figure 8. The frame at the 
ROPS-machine innerface deflected a maximum of 0.85 in and 
had a permanent deflection of 0.26 in. Table 6 shows the side 
load energy for each displacement. 

A load of 1,567,000 lb was applied to the ROPS during 
the vertical load test. As shown in figure 9, this resulted in a 
vertical deflection of 0.24 in. 



11 



800 



700 



600 - 



500 - 



to 
O 




d" 


400 


< 




o 




_i 




UJ 




Q 


300 



c/> 



200 



100 








I 2 3 4 5 6 7 8 £ 

DEFLECTION, in 

Figure 8. — Static test side load deflection curve, 390,000-lb-GVW, wheeled, front-end loader. 



10 




400 



VERTICAL LOAD, 10 lb 
Figure 9. — Static test vertical deflection curve, 390,000-lb-GVW, wheeled, front-end loader. 



12 



During the longitudinal load test a load of 659,000 lb was 
applied to the ROPS. The ROPS deflected >3 in and it 
absorbed 1,176,000 in*lb of energy. The load deflection curve 
for the rear load is shown in figure 10. The rear load energy is 
shown in table 6. The capacity of the hydraulic system was 
reached during the test, which prevented any higher loads from 
being reached. 



Table 6.— ROPS static test side and longitudinal load energy 



< 
o 



700 



600 - 



500 - 



400 - 




300 - 



200 - 



I 2 3 
DEFLECTION AT LOAD POINT, in 



Figure 10. — Static test longitudinal load deflection curve, 
390,000-lb-GVW, wheeled, front-end loader. 



Load, 
10 3 lb 



Displace- 
ment, in 



Av load, 
10 3 lb 



Energy, 10 3 in-lb 



Incremental 



Cumulative 



SIDE LOAD, 6.03-in FINAL DISPLACEMENT 






} 


43.19 


21.60 


21.60 


86.37 


.50 








86.37 


.50 } 


141.88 


71.65 


93.24 


197.40 


1.01 








197.40 


1.01 } 


345.58 


694.27 


787.51 


493.77 


3.01 








493.77 


3.01 } 


513.74 


252.76 


1,040.27 


533.70 


3.51 








533.70 


3.51 } 


551 .60 


273.59 


1,313.87 


569.50 


4.00 








569.50 


4.00 } 


581 .98 


293.32 


1,607.19 


594.47 


4.51 








594.47 


4.51 } 


599.84 


299.32 


1,906.51 


605.20 


5.01 








605.20 


5.01 } 


612.30 


307.99 


2,214.49 


619.40 


5.51 








619.40 


5.51 } 


626.18 


311.21 


2,525.70 


632.97 


6.01 








632.97 


6.01 } 


638.44 


321.14 


2,846.84 


643.90 


6.51 








643.90 


6.51 } 


648.04 


305.87 


3,152.71 


652.17 


6.98 








652.17 


6.98 } 


658.48 


346.36 


3,499.07 


664.80 


7.51 








664.80 


7.51 } 


672.54 


334.93 


3,834.00 


680.27 


8.00 








680.27 


8.00 } 


682.68 


345.44 


4,179.44 


685.10 


8.51 








685.10 


8.51 } 


342.55 


847.81 


3,331.63 





6.04 










LONGITUDINAL LOAD 


1.18-in FINAL DISPLACEMENT 





} 


39.14 


18.55 


18.55 


78.27 


0.47 








78.27 


0.47 } 


156.07 


76.47 


95.02 


233.87 


.96 








233.87 


.96 } 


308.78 


159.95 


254.97 


383.70 


1.48 








383.70 


1.48 } 


441.26 


217.98 


472.96 


498.83 


1.98 








498.83 


1.98 } 


544.23 


269.94 


742.90 


589.63 


2.47 








589.63 


2.47 } 


621 .33 


311.29 


1,054.18 


653.03 


2.97 








653.03 


2.97 } 


656.20 


122.05 


1,176.23 


659.37 


3.16 








659.37 


3.16 } 


329.68 


-651.12 


525.12 



13 



TEST WITH 286,000-lb-GVW, WHEELED, FRONT-END LOADER 



The rollover test of the 286,000-lb-GVW, wheeled, front- 
end loader (test 5) met the objectives of the test. Data were 
obtained to determine the magnitudes and directions of load- 
ing on the ROPS. The machine rolled two complete revolu- 
tions and subjected the ROPS to two impacts on the roll hill. 
An additional ROPS impact occurred when the machine came 
to rest on its side on the road at the bottom of the hill as shown 
in figure 1 1 . This impact was softened because the road had 
been ripped prior to the roll. In addition, the tires had blown 
out on the machine, which caused a large decrease in its roll 
rate prior to impact. The only damage to the machine frame or 
ROPS mounts that was observed was the blown tires and bent 
rims on the left side of the machine. 

During the roll the longitudinal centerline of the machine 
remained perpendicular to the vertical centerline of the hill. 



This resulted in low longitudinal loading on the ROPS. A 
summary of the ROPS loading is given in table 7. 

The displacement potentiometers provided data to deter- 
mine loads for the side and longitudinal direction. Accelerom- 
eter data were used to obtain loads for the vertical direction. 
The strain gauges provided impact load data for the vertical, 
side, and longitudinal directions. The strain gauges provided a 
means to determine the loads at a standard method of data 
reduction. The reduction of the accelerometer data required 
consideration of the machine dynamics in order to obtain 
meaningful results. The potentiometer data were corrected for 
the geometery effects in their readings caused by the location 
of the potentiometers. 

The ROPS side loading during the first two impacts on 
the roll hill was much lower than expected. In order to obtain 




Figure 11. — Roll test 5, 286,000-lb-GVW, wheeled, front-end loader. Note that an anthropometric dummy was strapped in the cab 
to evaluate the Bureau's Vest Restraint System. 



14 



an understanding of the low side loads a quantative analysis 
was conducted of the following factors that influence the 
dynamics of a roll: 

Machine mass. 

Radius of gyration. 

Location of the center of gravity. 

Distance of the ROPS from the center of gravity. 

Change in roll rates during impacts. 

Translational velocity of the machine. 

Penetration resistance of the roll hill. 

A review of these factors does not indicate any gross 
difference with the previous roll tests that would explain the 
low loads. It appears that the major difference in the factors is 
the location of the center of gravity. The 286,000-lb-GVW 
machine appears to have a much lower center of gravity. The 
machines previously tested rolled off the tilt table at approxi- 
mately a 50° angle. However, this machine rolled off at 
approximately a 65° angle and entered the first impact at a 
slightly higher rotational velocity. From an analysis of the 
films it appears that the machine was in a more vertical 
position when the first impact occurred. 

An examination of the overall configuration of the ROPS 
and the ROPS-machine configuration does suggest some 
differences which may account for the low loads. For example, 
the ROPS on the 286,000-lb-GVW machine differs from the 
390,000-lb machine in overall dimensions such as follows: 

Smaller plan view area because of slanted posts and the 
location of the operator within the ROPS. 

Smaller side profile area (no crossmember and shorter 
length) because of the plate construction. 

Also, overall machine parameters, such as ROPS-machine 
width ratio and ROPS-machine height, differed between the 
machines tested. 

A qualitative comparison of these factors for various 
machines presently available may indicate that there are sig- 
nificant differences between the 286,000-lb-GVW machine 
with the present ROPS configuration and the other machines. 

A review of the motion picture coverage of the test 
indicates that the generally smaller profile of this ROPS, 
especially the thin (1 in) top plate, may have resulted in the 



Table 7.— Fifth roll test summary 

(286,000-lb-GVW, wheeled, front-end loader) 

1st impact 2d impact Bench impact 

MEASURED 

Vertical load, 10 3 lb: 

ROPS strain gauges 562 559 NAp 

Accelerometer 313 627 NAp 

Side load, 10 3 lb: 

ROPS strain gauges 226 192 NAp 

ROPS deflection 1 180 180 NAp 

Longitudinal load, 10 3 lb: 
ROPS strain gauges 65 90 NAp 

Roll rate, °/s: 

Before impact: Gyroscope 125 241 NAp 

After impact: Gyroscope 63 165 NAp 

Max ROPS penetration, in: 

Field measurement 22 38 NAp 

ESTIMATED 2 

Vertical load: 

Force 10 3 lb.... 562 559 <7.3 

Force pet GVW.... =197 196 <3 

Side load: 

Force 10 3 lb.... 226 192 <52 

Force pet GVW.... 79 67 <18 

Longitudinal load: 

Force 10 3 lb... 65 90 <12.8 

Force pet GVW.... 23 32 <8 

Side deflection in.... 1 1 NAp 

Longitudinal deflection in.... 0.6 ND NAp 

NAp Not applicable. ND Not determined. 

1 Computer load deflection curve. 

2 Data are rounded. 

ROPS slicing through the soil and offering very little lateral 
area to develop a side force. On the first impact the ROPS 
posts left a clear imprint in the hill indicating the side forces 
developed lower on the top plate. This is clearly seen for the 
first 0.05 s where little side load was experienced. For this time 
period only the top plate was in contact with the ground. 



CONCLUSIONS 



It should be recognized that ROPS performance criteria 
do not guarantee protection of the operator in all cases. From 
the testing conducted during this program for example, it 
appears that when machines lose contact with the hill and 
become airborne, even larger forces and energy demands are 
imposed upon the ROPS structure. Thus, care must be taken 
to ensure that test conditions and/or field usage do not 
invalidate performance criteria. 

A longitudinal force and energy capability has never been 
specifically addressed in ROPS performance criteria. Al- 
though the tests conducted for this program were designed to 
provide maximum side loading and only minimum longitudi- 
nal loading, longitudinal loads were recorded for each test. 
With the exception of one ROPS impact, the longitudinal 
loads were relatively low in comparison to the side load. The 
second ROPS impact of test 3 did cause the ROPS to fail 
because of the location of the longitudinal load resulting from 
the orientation of the machine relative to the downward slope 
of the roll hill. 



Larger longitudinal loads than were observed during the 
roll tests are possible in an actual field rollover. For example, if 
prior to a rollover a machine was being operated in one of the 
following situations larger longitudinal loads could result: 

1 . In a position pointing slightly uphill or downhill. 

2. If an operator abruptly changed steering direction. 

3. If the machine was traveling at an appreciable forward 
or aft velocity. 

4. If a small machine was suddenly accelerated causing 
rear upset because of rotation about the powered axle. 

5. In an accident during loading or unloading onto a 
lowboy truck. 

In any case, it would be anticipated that the principal roll 
axis would rapidly revert to the longitudinal axis of the 
machine, thus subjecting the ROPS to greater side loads than 
longitudinal loads. Therefore, the longitudinal loading and 
energy criteria should be equal to or less than the side load 
capability. It is believed that a longitudinal force that is 80 pet 



15 



of the side criteria would be adequate for 540° rolls (two top result of the high vertical stiffness and load carrying capability 

and two side loads). required to meet load and energy criteria in the critical side 

The other major performance factor to be considered is direction. A ROPS generally has a vertical capability in excess 

the vertical load. SAE J1040c criteria currently require a of 200 pet GVW and maybe as high as 1,000 pet GVW even 

minimum 200-pct-GVW vertical load for all machine types though the roll test data indicate actual maximum vertical 

and masses. This requirement is usually met or exceeded as a loads of only 200 to 400 pet GVW. 



INT.-BU.OF MINES,PGH.,PA. 28843 

U.S. GOVERNMENT PRINTING OFFICE: 611-012/00,013 



m 

z 


"0 ID 


O 


T3(DC 


£P 


o 
o 

3" 


O 
Q. 


CD • 


?o 


.3 O 


CO 


C 

o 


c CD 


<3 




o' 

3 


O T3 


So 


8070 
PA 15 


S 


0° 


1 3 


IALI 

RPR 


DO 
o 


D 
to" 


CD <J> 

o 


> C 


ro 

CO 


Q. 


C 


3- 


H (/> 






o" 


CD 


25 






3 


5" 


Si m 








CD 



i 

CO 

o 
o 



0) 



m 
D 

c 
> 

i - 

o 

"D 
O 
3D 

H 
C 
Z 



m 



O 

-< 
m 

DO 



C 91 89 ** 










* 













"o V 








•TV *2» 

















?•%. '• 











/ 



^°A 















L^ ^ . 



^0 









c *.-iife-"* < ? 







° ^P ,^ 






































S? ^ 




A V 



















A V ^ 
** ^ 





r oV 





'* o 



•-• ^ v 7 ^* */ %^-\^ %.-^\# %'tt % '4r 

% / :H' : V -'W' V* -lit V -*W" V* : ll6 V 1 




^ 







^ 







^ A^ 






"<>**" "-*.»** <\- H . <* 



v oV* 



JP^ A 































4- V V 





J ^ 



^"V 
V ^ 






.^i^, ^° ^. 




40. 




^°^ v 













\v _ „ _ #T, 



**% 3 



V* -Mm-. %s :28fc \/ -Mix %s A \/ 



• ">?„ A 







C.VP 




6 «A V ^ - 



















^d* 



.4 0. 




^ * 








4> e, " » , 



,0 



A, 



.0 ^* 




















K^^> 4 °> & *" 



^ ^ 




<. *^.«* ,G 



^ ^ 







H EC KM AN IXJ 
BINDERY INC. |e| 

#FEB 89 
N. MANCHESTER, 
INDIANA 46962 






























*°«* »S»»' JP VI 



^^ . 





4 0t 



■^ 




